Macro rquickjs_core::async_with

macro_rules! async_with {
    ($context:expr => |$ctx:ident| { $($t:tt)* }) => { ... };
}

Available on crate feature futures only.

A macro for safely using an asynchronous context while capturing the environment.

Usage

let rt = AsyncRuntime::new().unwrap();
let ctx = AsyncContext::full(&rt).await.unwrap();

// In order for futures to conver to javascript promises they need to return `Result`.
async fn delay<'js>(amount: f64, cb: Function<'js>) -> Result<()> {
    tokio::time::sleep(Duration::from_secs_f64(amount)).await;
    cb.call::<(), ()>(());
    Ok(())
}

fn print(text: String) -> Result<()> {
    println!("{}", text);
    Ok(())
}

let mut some_var = 1;
// closure always moves, so create a ref.
let some_var_ref = &mut some_var;
async_with!(ctx => |ctx|{
     
    // With the macro you can borrow the environment.
    *some_var_ref += 1;

    let delay = Func::new("delay", Async(delay));

    let global = ctx.globals();
    global.set("print",Func::from(print)).unwrap();
    global.set("delay",delay).unwrap();
    ctx.eval::<(),_>(r#"
        print("start");
        delay(1,() => {
            print("delayed");
        })
        print("after");
    "#).unwrap();
}).await;
assert_eq!(some_var,2);

rt.idle().await